I. Field of the Invention
The invention relates generally to a device designed for human or animal use in biological imaging procedures such as: computed tomography, sonography, and magnetic resonance imaging. The invention also relates to the use of such a device.
II. Prior Art
A. Compression Devices
Compression devices are devices which compress parts of the body for diagnostic purposes as will be subsequently described herein. Such compression devices are available for use, for example, in fluoroscopic procedures (real time visualization of body parts by use of x-rays) and in mammography (breast x-rays). Compression devices may be either balloon type or rigid type, and may be used by hand or by remote control.
With reference to FIGS. 1 and 2, an example of the most commonly used compression device, termed a "paddle", will be described. It is of the balloon type and is used by hand during the performance of fluoroscopic procedures such as an upper gastrointestinal series or barium enema. As shown in FIG. 1, the paddle (1) consists of a rubber balloon or bladder (2) which is attached to a rigid backing (3). The balloon is connected via rubber tubing encased in a long rod (4) to a an inflation bulb (5). The air flow is controlled by a valve (6). If the valve is closed, squeezing the inflation bulb repeatedly, will insufflate the rubber balloon with room air such that it forms a hemispherical shape. The device is held at the handle grip (7), with the rubber bladder facing downward, allowing the user to position the rubber bladder, for example, on a patients abdomen (8) within the x-ray beam, under fluoroscopic guidance. The length of the rod permits the user to keep his hand at a distance, outside the x-ray beam. FIG. 2 is a head on view of a patient (9), lying flat on an x-ray table (10). The tower (11), contains the parts which produce the x-rays. The tower can be moved up and down on an armature (12), by holding the handle (13) and moving it in the desired direciton. Compression of the abdomen is achieved in one of two ways. In one method the user's hand (19) exerts a downward force on the compression device's handle grip (7). This manual downward force compresses the patient's abdomen (8) between the balloon and the table. Alternately, compression is achieved by first positioning the balloon over the desired patient part with one hand (19). Then with the user's other hand (14), moving the tower downward, such that the weight of the tower plus the downward force applied to the tower's handle, exert a downward force on the back of the paddle's rigid backing (3), thus compressing the patient's abdomen between the table and the balloon.
Another balloon type of compression device is the "compression bladder." With reference to FIG. 3 the usage of a compression bladder will be described. The compression bladder consists of a circular or rectangular rubber balloon (20) with a segment of tubing (21). A valve (22) is attached to the tubing, to which an inflation bulb (23) is attached. The bladder is positioned in the desired location on the patient's body (24) shown in cross section. It is then secured in place by a compression band (25) which is tied around the patients body and secured, for example, by velcro. Compression is then achieved by insufflating the rubber bladder with room air by repeatedly squeezing the inflation bulb. The inflated bladder compresses the body since it is fixed in place by the band. This is often used to provide pinpoint pressure, for example, during kidney x-rays (excretory urography) for compressing the ureters.
A rigid compression device is generally known as a compression cone. With reference to FIGS. 4 and 5 a compression cone will be described. The compression cone is designed to be attached to an x-ray machine (50), but not directly to a patient. It can be used as a hand-assisted device attached to an x-ray tower (51), or as a remote controlled compression device. It consists of a cone or rectangular shaped elevated portion (40), which lacks a hole, attached to a base plate (41). The base plate attaches to the tower (51) of the x-ray machine. Compression is applied by positioning the patient (52) such that the desired body part (53) is directly under the cone, and moving the tower downward to squeeze the body between the table top (54) and the tower (51). Alternately, not shown in these figures, the cone is attached to a separate mechanized arm which can be positioned by remote control and also moved up and down by remote control to effect variable compression. The use of remote control allows the radiologist to perform the procedure without exposing himself to scatter radiation in the examining room.
There are also flat, rigid compression devices, devised specifically for compression of the breast during mammography. The purpose of compression of the breast in mammography includes: separating structure within the breast, reducing the distance between the x-ray film and the breast, and reducing overall thickness of the breast to get a better quality picture with less radiation. With reference to FIG. 6 a flat mammography compression device will be described. This device is composed of a generally flat, rectangular plate (60) attached to a frame (61). The frame in turn, is attached to an arm (62), connecting the device to part of the tower (63). Some models allow for angulation of the compression plate as well (not shown in this figure). Compression the breast against a platform (65) is achieved by manually adjusting the arms and sliding the flat plate downward, and locking the adjustment lever. The flat shape of the plate is desirable for compressing a small, soft structure, such as the breast. It would be undesirable for compressing an abdomen. Some similar devices are not attached to the mammography unit, but are mounted to it by suction cups, or tied to the platform with a strap. After the device is positioned, x-rays are produced from the x-ray tube within the housing (66), producing an exposure of the cassette place within the platform (65).
B. Mammography Compression Biopsy Guides
A biopsy is a procedure whereby a sample of biologic tissue is obtained, usually by placement of a needle designed to trap tissue, or by attaching a syringe to the needle and suctioning. Needles are commonly placed in breast tissue, either for biopsy, or to remain in the breast and serve as a guide to surgery.
The only device which both compresses tissue and serves as a portal for a biopsy, is a mammography localization device for biopsy. With reference to FIG. 7 an example of a mammography localization device for biopsy will be described. In this example, this device is identical in shape and in attachment to the mammography machine as shown in FIG. 6. FIG. 7 also shows the compression plate (70), frame (71), arm (72), part of the tower (73) and the platform (74). The critical difference in FIG. 7 is a rectangular cut-out which serves as the biopsy portal (75). At the edges of the portal, there are lines (76) etched into the device, which are radiopaque (can show up on x-ray film). These lines serve as a graph to guide placement of the needle. One row serves as an "x-coordinate" and the other row as a "y-coordinate" in localizing the mass on the developed x-ray film. The radiologist then enters the room, and uses these lines on the device as an optical guide to select the site on the patient's skin most likely to be directly overlying the breast mass.
With respect to mammography biopsy localizers, there are other designs, which may form a radiopaque grid over the biopsy portal. Some devices may not attach to the mammography machine tower, but rather to the platform by use of suction cups on a series of supporting arms. Some devices are placed over the breast, and tied around the platform to secure them.
C. Imaging Biopsy Guides
Cross sectional imaging procedures are methods that visualize a "slice" of internal anatomy. An example of an imaging procedure is computed tomography (CT). CT is a method whereby x-rays and computers are combined to produce a picture of a "slice" of a body. Percutaneous (through the skin) procedures are interventional procedures whereby a needle, catheter or similar appliance ia placed internally via a skin puncture, usually under radiologic guidance. Radiologic guidance may include, for example, fluoroscopy, or cross sectional imaging procedures, such as CT, ultrasound, and magnetic resonance imaging (MRI). For example, the placement of a needle, for the biopsy of an internal body part often requires CT guidance to place the needle tip in the desired internal location. CT and ultrasound are commonly used to guide placement needles for biopsies or similar procedures. Using the example of a CT guided biopsy, the method is as follows. A CT scan is first performed to localize a mass. Each CT "slice" is labelled by the position of the table or patient with respect to the gantry (x-ray portal). The slice showing the mass is selected and used to chose an anatomic approach for needle placement. With the x-ray off, the radiologist enters the room and using standard sterile technique, places the needle through the skin overlying the mass. The CT slice is repeated to prove that the needle has in fact been successfully placed within the mass.
Difficulty in needle placement may arise due to a variety of reasons. Firstly, it may be desirable to avoid some structures in the ideal needle path, forcing use of a less desirable path. Secondly, a desirable needle path may not be usable due to a surgical appliance or skin lesion overlying the lesion. Thirdly, a long needle path may make accurate placement with a minimum number of tries, difficult. This is because of the geometry of the patient; if there is a longer distance from the skin to the mass, a minor "off-course" angulation at the skin insertion site is amplified at the needle tip. Thus a small mass may require a number of needle passes until it is punctured placed. This problem is accentuated when performing percutaneous procedures on obese individuals.
A number of devices have been devised to assist in accurate imaging or CT guided needle placement. For example, a grid that shows up on CT images may be placed over the patient's skin to assist in locating the skin directly overlying a lesion. Another example is a stabilization device for intracranial CT guided biopsy (published in RADIOLOGY 144:183-184,1982). This device stabilizes the head within a ring-frame, with an adjustable needle guide along the upper circumference of the frame. Another example is the use of injected carbon dioxide (relatively harmless in the abdominal cavity), to move internal structures blocking the most desirable needle path, out of the way (published in RADIOLOGY 161:829-830,1986).
None of the existing devices used in cross sectional imaging percutaneous procedures, allow the operator to move internal structures out of the way by using compression. None of the existing compression devices are designed for use in cross-sectional imaging procedures. Only the mammography biopsy localization device combines compression with a biopsy portal. Unlike this invention, the mammography biopsy guide is not designed for use in cross sectional imaging, it is not shaped to provide compression to deep structures, and does not attach independently to the patient's body. For example, since the mammography biopsy guide is flat, it will not provide adequate compression for a patients abdomen.